부산대학교 도서관

The carrier phase-shift PWM strategy is widely used in modular multilevel converters to satisfy the driver demands of the numerous switches in submodules. However, the traditional carrier phase-shift PWM strategy can cause an imbalance phenomenon in the submodule capacitor voltages, which deteriorates the system working performance. This study develops a mathematical model of an MMC system, which is the basis of a quantitative analysis of the relations between the PWM strategy and the imbalance phenomenon. A novel method is then proposed to provide an accurate description of the cause of the imbalance phenomenon in relation to the PWM strategy. Based on the above analysis, a quantitative analysis of the imbalance phenomenon in the capacitor voltages is used to further measure the magnitudes of the imbalance phenomenon. The effect of the PWM strategy on the capacitor voltages is finally demonstrated via experiments.